U.S. patent application number 13/696057 was filed with the patent office on 2013-12-19 for remote phosphor tape lighting units.
This patent application is currently assigned to NEXT LIGHTING CORO.. The applicant listed for this patent is Eric Bretschneider. Invention is credited to Eric Bretschneider.
Application Number | 20130334956 13/696057 |
Document ID | / |
Family ID | 44904483 |
Filed Date | 2013-12-19 |
United States Patent
Application |
20130334956 |
Kind Code |
A1 |
Bretschneider; Eric |
December 19, 2013 |
REMOTE PHOSPHOR TAPE LIGHTING UNITS
Abstract
The invention provides systems and methods relating to remote
phosphor tapes and methods of making and using the same. A remote
phosphor tape may be used in lighting units. The phosphor tape may
comprise a front side and a backside. The phosphor tape may have a
phosphor layer comprising a phosphor material configured to emit
light of an emission wavelength when illuminated by light of an
excitation wavelength. The remote phosphor tape is configured for
use as a remote phosphor in a lighting unit.
Inventors: |
Bretschneider; Eric;
(Bowling Green, KY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bretschneider; Eric |
Bowling Green |
KY |
US |
|
|
Assignee: |
NEXT LIGHTING CORO.
|
Family ID: |
44904483 |
Appl. No.: |
13/696057 |
Filed: |
May 5, 2011 |
PCT Filed: |
May 5, 2011 |
PCT NO: |
PCT/US2011/035376 |
371 Date: |
August 30, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61331638 |
May 5, 2010 |
|
|
|
Current U.S.
Class: |
313/498 ; 252/1;
428/195.1; 428/343; 428/457 |
Current CPC
Class: |
H01L 2933/0041 20130101;
H01L 33/505 20130101; Y10T 428/31678 20150401; F21K 9/64 20160801;
H01L 33/507 20130101; Y10T 428/28 20150115; Y10T 428/24802
20150115 |
Class at
Publication: |
313/498 ;
428/195.1; 428/457; 428/343; 252/1 |
International
Class: |
F21K 99/00 20060101
F21K099/00 |
Claims
1. A remote phosphor tape for use in lighting units, comprising: a
front side; a backside; and a phosphor layer comprising a phosphor
material configured to emit light of an emission wavelength when
illuminated by light of an excitation wavelength, wherein said
remote phosphor tape is configured for use as a remote phosphor in
a lighting unit.
2. The remote phosphor tape of claim 1, wherein the phosphor layer
further comprises a polymeric binder material.
3. The remote phosphor tape of claim 1, further comprising a
substrate layer.
4. The remote phosphor tape of claim 3, wherein the phosphor layer
is deposited on the substrate layer through one of a chemical or
physical vapor deposition technique.
5. The remote phosphor tape of claim 3, wherein the phosphor layer
is disposed on the substrate layer through a printing
technique.
6. The remote phosphor tape of claim 3, wherein the substrate layer
is reflective.
7. The remote phosphor tape of claim 6, wherein the substrate layer
is diffusely reflective.
8. The remote phosphor tape of claim 1, further comprising a
pressure sensitive adhesive layer disposed adjacent to the back
side of the phosphor tape.
9. The remote phosphor tape of claim 1, wherein the phosphor tape
is flexible.
10. A lighting unit, comprising: at least one light emitting
element, configured to emit a light of at least one excitation
wavelength when illuminated; a support structure spatially
separated from the at least one light emitting element; and a
remote phosphor tape disposed on said support structure, the remote
phosphor tape comprising: a front side; a back side; and a phosphor
layer comprising a phosphor material configured to emit light of a
emission wavelength when illuminated by the light of at least one
excitation wavelength, wherein the at least one light emitting
element and the remote phosphor tape are positioned such that a
portion of the light of at least one excitation wavelength emitted
by the at least one light emitting element is received by the
phosphor layer in the remote phosphor tape.
11. The lighting unit of claim 10, wherein the support structure is
at least partially reflective.
12. The lighting unit of claim 10, wherein the remote phosphor tape
further comprises a substrate layer adjacent to the phosphor
layer.
13. The lighting unit of claim 12, wherein the substrate layer is
substantially reflective.
14. The lighting unit of claim 13, wherein the substrate layer is
diffusely reflective.
15. The lighting unit of claim 10, further comprising an optical
element configured to receive and redirect light emitted and
reflected by the remote phosphor tape into a region of desired
illumination.
16. The lighting unit of claim 10, wherein the at least one light
emitting element is a light emitting diode.
17. The lighting unit of claim 10, wherein the at least one light
emitting element is a white light emitting element.
Description
CROSS-REFERENCE
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/331,638, filed May 5, 2010, which application is
incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] Aspects of the invention relate to techniques and materials
that can be used to process radiant energy from light emitting
elements such as light emitting diodes using remote phosphors in a
tape form, typically so as to produce substantially white light of
desired characteristics.
BACKGROUND OF THE INVENTION
[0003] Solid state light emitters, such as light emitting diodes
(LEDs), are being developed for use in general illumination
applications due to their long lifetimes and high efficiencies.
However, the efficiency and lifetimes are reduced by typical
methods used to create a desirable white light for
illumination.
[0004] There are two main approaches to making white light using
LEDs. One approach uses direct emission from multiple monochromatic
LEDs. Typically, this approach requires electro-optical devices to
control the blending the light emitted by red, green, and blue
(RGB) LEDs. A second, more developed approach uses phosphor
converted LEDs (pcLEDs) to create white light. In this approach,
white LEDs are typically created using blue emitting chips coated
with a yellow phosphor, or a near-UV emitting chip coated with a
tri-phosphor blend of red, green and blue emitting phosphors. The
phosphor absorbs the blue- or near-UV light from the LED and
re-emits it at a different, longer wavelength such that white light
can be obtained. However, about half of the photons produced by the
phosphor are diverted back toward the LED chip where much of the
light is lost due to absorption, and the phosphor lifetime and
efficiency is compromised by the proximity of the phosphor material
to the heat-generating LED device, which leads to thermal
degradation of the phosphor. Thermal degradation of the phosphor in
turn can lead to a lack of color consistency of the LED device over
time. Furthermore, phosphor deposition must be precisely controlled
to produce LED devices having a consistent white color. Phosphor
deposition processes for remote phosphor applications may be
difficult to obtain in certain device configurations, or deposition
processes may be inefficient, causing a loss of expensive phosphor
material.
[0005] Hence, a need exists for more effective techniques and
materials to facilitate the use of phosphors as wavelength
converting materials in lighting devices to produce white light of
desirable quality. Features of high quality white light for
illumination can include high color rendering index (CRI), a
desired correlated color temperature (CCT), color consistency with
time, and color consistency between devices.
SUMMARY OF THE INVENTION
[0006] Aspects of the invention relate to remote phosphor tape for
use in lighting units. The remote phosphor tape may comprise a
front side, a back side, and a phosphor layer comprising a phosphor
material configured to emit light of an emission wavelength when
illuminated by light of an excitation wavelength. The phosphor tape
is configured for use as a remote phosphor in a lighting unit. The
phosphor layer may comprise a combination of one or more phosphor
materials in a binder material or disposed on a substrate
layer.
[0007] The invention also relates to lighting units comprising such
a remote phosphor tape. The lighting unit may comprise at least one
light emitting element, configured to emit a light of at least one
excitation wavelength when illuminated, a support structure
spatially separated from the light emitting element, and a remote
phosphor tape disposed on the support structure. The light emitting
element and the remote phosphor tape are positioned such that a
portion of the light emitted by the light emitting element is
received by the phosphor layer in the remote phosphor tape.
[0008] An aspect of the invention is directed to a remote phosphor
tape for use in lighting units. The remote phosphor tape may
comprise a front side; a backside; and a phosphor layer comprising
a phosphor material configured to emit light of an emission
wavelength when illuminated by light of an excitation wavelength,
wherein said remote phosphor tape is configured for use as a remote
phosphor in a lighting unit.
[0009] A lighting unit may be provided in accordance with another
aspect of the invention. The lighting unit may comprise at least
one light emitting element, configured to emit a light of at least
one excitation wavelength when illuminated; a support structure
spatially separated from the at least one light emitting element;
and a remote phosphor tape disposed on said support structure, the
remote phosphor tape comprising a front side; a back side; and a
phosphor layer comprising a phosphor material configured to emit
light of a emission wavelength when illuminated by the light of at
least one excitation wavelength, wherein the at least one light
emitting element and the remote phosphor tape are positioned such
that a portion of the light of at least one excitation wavelength
emitted by the at least one light emitting element is received by
the phosphor layer in the remote phosphor tape.
[0010] Other goals and advantages of the invention will be further
appreciated and understood when considered in conjunction with the
following description and accompanying drawings. While the
following description may contain specific details describing
particular embodiments of the invention, this should not be
construed as limitations to the scope of the invention but rather
as an exemplification of preferable embodiments. For each aspect of
the invention, many variations are possible as suggested herein
that are known to those of ordinary skill in the art. A variety of
changes and modifications can be made within the scope of the
invention without departing from the spirit thereof.
INCORPORATION BY REFERENCE
[0011] All publications, patents, and patent applications mentioned
in this specification are herein incorporated by reference to the
same extent as if each individual publication, patent, or patent
application was specifically and individually indicated to be
incorporated by reference.
BRIEF DESCRIPTION OF THE FIGURES
[0012] The novel features of the invention are set forth with
particularity in the appended claims. A better understanding of the
features and advantages of the present invention will be obtained
by reference to the following detailed description that sets forth
illustrative embodiments, in which the principles of the invention
are utilized, and the accompanying drawings of which:
[0013] FIG. 1A is a schematic cross-sectional view of a remote
phosphor tape, wherein the phosphor is embedded in a polymeric
binder material.
[0014] FIG. 1B is an alternative cross-sectional view of a remote
phosphor tape.
[0015] FIG. 2A is a schematic cross-sectional view of a remote
phosphor tape wherein a phosphor layer is disposed on a reflective
tape.
[0016] FIG. 2B is an alternative cross-sectional view of a remote
phosphor tape wherein a phosphor layer is disposed on a reflective
tape.
[0017] FIG. 2C is an additional cross-sectional view of a remote
phosphor tape mounted on a substrate.
[0018] FIG. 3 is a perspective view of a roll of remote phosphor
tape.
[0019] FIG. 4 is a schematic cross-sectional view of a piece of
remote phosphor tape being applied to an example support structure
in an illustrative lighting unit.
[0020] FIG. 5 is a schematic cross-sectional view of an
illustrative lighting unit comprising a reflective remote phosphor
tape.
[0021] FIG. 6a is a perspective view of another lighting unit
comprising a remote phosphor tape.
[0022] FIG. 6b is a schematic cross-sectional view of the lighting
unit of FIG. 6a comprising a remote phosphor tape.
[0023] FIG. 7 is a schematic cross-sectional view of another
lighting unit comprising a substantially transparent remote
phosphor tape disposed on a narrow support structure.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0024] While preferable embodiments of the invention have been
shown and described herein, it will be obvious to those skilled in
the art that such embodiments are provided by way of example only.
Numerous variations, changes, and substitutions will now occur to
those skilled in the art without departing from the invention. It
should be understood that various alternatives to the embodiments
of the invention described herein may be employed in practicing the
invention.
[0025] Aspects of the invention relate to remote phosphor tapes and
methods of making and using the same. All references cited in this
application are hereby incorporate by reference in their entirety.
In particular, the disclosure of the following: U.S. Provisional
Application, "Lighting unit having lighting strips with light
emitting elements and a remote phosphor material" filed Feb. 17,
2010 having Ser. No. 61/338,268; U.S. patent application, "Lighting
Unit Having Lighting Strips with Light Emitting Elements and Remote
Luminescent Material" filed Feb. 16, 2011 having Ser. No.
13/029,000, are hereby incorporated by reference in their
entirety.
[0026] The invention provides systems and methods for remote
phosphor tapes which may be used in providing illumination. Various
aspects of the invention described herein may be applied to any of
the particular applications set forth below or for any other types
of lighting units or lighting strips. The invention may be applied
as a standalone system or method, or as part of an integrated
illumination system. It shall be understood that different aspects
of the invention can be appreciated individually, collectively, or
in combination with each other.
TERMINOLOGY
[0027] The term "color" as used herein can mean a wavelength or any
combination of monochromatic light in the visible range of
electromagnetic radiation, such as red, orange, yellow, green,
blue, violet, or white, or a wavelength in the near infrared range,
or the ultraviolent (UV) range of light. Electro-luminscence (EL)
devices can emit light of a plurality of wavelengths and their
emission peaks can be very broad or narrow.
[0028] The term "plurality" has the meaning of "one or more".
[0029] The term "adjacent to" as used herein denotes a relative
positioning of two articles that are near one another. Adjacent
items can be touching, or separated by one or more layers.
Remote Phosphor Tape
[0030] Aspects of the invention relate to tape comprising phosphor
material which is configured to be used as a remote phosphor in
lighting units to color-convert light from at least one light
emitting element to light with desirable color characteristics. The
term phosphor as referred to herein refers to any phosphor material
or combination of materials that phosphoresces or fluoresces when
excited by light from the light emitting elements. The term
phosphor and phosphor material are used interchangeably herein. The
phosphor material can be an inorganic material, an organic
material, or a combination of inorganic and organic materials. The
phosphor material can be a quantum-dot based material or
nanocrystal. Numerous phosphor material formulations can be used
dependent on the excitation spectra provided by the light emitting
elements and the output light characteristics desired. For example,
when the light emitting elements provide an emission spectrum
yielding white light with a high correlated color temperature,
phosphors emitting light of a red and/or orange wavelength can be
used to achieve lower/warmer correlated color temperature white
light and to improve the color rendering index. Developments in
luminescent materials and applications are generally described in
Adrian Kitai, Luminescent Materials and Applications, Wiley (May
27, 2008) and Shigeo Shionoya, William Yen, and Hajime Yamamoto,
Phosphor Handbook, CRC Press 2nd edition (Dec. 1, 2006), which are
hereby incorporated by reference in their entirety.
[0031] A remote phosphor refers to a phosphor material that is not
inside or in physical contact with the light emitting element that
is used to excite the phosphor material. For lighting units
comprising one or more light emitting diodes (LEDs), a remote
phosphor is spatially separated from the LED package. One advantage
of using a remote phosphor is that color consistency of a lighting
unit product can be enhanced through control of the formulation and
deposition of the phosphor material. For instance, when LEDs are
fabricated they are binned according to their color
characteristics. LEDs from different bins can be used in production
of lighting units without sacrificing product to product color
consistency if the quantity and formulation of the phosphor
material is adjusted depending upon the exact spectral power
density provided by LEDs.
[0032] Another advantage of using a remote phosphor material is
that there is reduced thermal quenching of the phosphor material
because it is physically displaced from the heat generating LED
package. Thus, the color of the light is more consistent with
lifetime and operating temperature. In comparison, in a luminaire
that employs a typical warm white LED, the red and/or orange
phosphor material is in direct contact with the LED package and
will quench rapidly as the LED is operated at higher temperature
resulting in a noticeable shift in color point.
[0033] A further advantage of using a remote phosphor material is
that to achieve a warmer color temperature, the selection of the
phosphor material is not limited only to materials that can operate
well at higher temperatures. This can open up a range of materials
that are not available to typical LED configurations. Still another
advantage of using a remote phosphor material is an increased
phosphor material lifetime due to the decreased operating
temperature.
Phosphor in Binder
[0034] In one embodiment of the invention, the remote phosphor tape
comprises a phosphor layer which is formed using a combination of
one or more phosphor materials mixed in a binder material. FIG. 1A
is a schematic cross-sectional view of an example of such a remote
phosphor tape 100 having a front side 110 and a back side 120. The
remote phosphor tape 100 includes a phosphor layer 130 comprising a
combination of one or more phosphor materials and a substantially
transparent polymeric binder material. A pressure sensitive
adhesive (PSA) layer 140 and a release liner 150 may optionally be
disposed adjacent the back side 120 of the remote phosphor tape
100. A protective layer 160 may be disposed on the front side 110
of the remote phosphor tape to protect the phosphor layer 130. Any
of the phosphor layer 130, pressure sensitive adhesive layer 140,
release liner 150, or protective layer 160 need not be continuous
layers.
[0035] FIG. 1B provides an alternative cross-sectional view of a
remote phosphor tape. A remote phosphor tape 100 may have a front
side 110 and a back side 120. The remote phosphor tape may have a
phosphor layer 130 comprising a combination of one or more phosphor
materials and a substantially transparent polymeric binder
material. A release liner 150 may optionally be provided adjacent
to the back side 120 of the phosphor tape. The release liner may
directly contact the phosphor layer. A protective layer 160 may be
disposed on the front side 110 of the remote phosphor tape to
protect the phosphor layer 130. Any of the phosphor layer 130,
release liner 150, or protective layer 160 need not be continuous
layers.
Remote Phosphor Tape Comprising Substrate Layer
[0036] FIG. 2A is a schematic cross-sectional view of an example of
a substantially transparent remote phosphor tape 200 having a front
side 210 and a back side 220. The remote phosphor tape 200 includes
a phosphor layer 230 comprising a combination of one or more
phosphor materials disposed on a substrate layer 235. The phosphor
layer may further comprise a binder material. A pressure sensitive
adhesive layer 240 and a release liner 250 may optionally be
disposed adjacent the back side 220 of the remote phosphor tape
200, such that the substrate layer is sandwiched between the
phosphor layer and the pressure sensitive adhesive layer. A
protective layer 260 may be disposed on the front side 210 of the
remote phosphor tape to protect the phosphor layer 230. Additional
layers may also be included in the phosphor tape. At least one of
the substrate layer 235 or the protective layer 260 is
substantially transparent to visible light, such that excitation
light may reach the phosphor layer and light generated by the
phosphor layer may exit the remote phosphor tape. Any of the
phosphor layer 230, substrate layer 235, pressure sensitive
adhesive layer 240, release liner 250, or protective layer 260 need
not be continuous layers. In particular, the phosphor layer need
not be continuous. Some regions of the substrate layer may be
coated with phosphor material while other regions are not coated.
For example, the phosphor layer may be printed onto the substrate
layer and the phosphor materials may form a pattern on the
tape.
[0037] FIG. 2B provides a cross-sectional view of an example of a
substantially transparent remote phosphor tape 200 having a front
side 210 and a back side 220. The remote phosphor tape 200 may
include a phosphor layer 230 comprising a combination of one or
more phosphor materials disposed on a substrate layer 235. The
phosphor layer may further comprise a binder material. A release
liner 250 may optionally be disposed adjacent the back side 220 of
the remote phosphor tape 200, such that the substrate layer may
directly contact the release liner. A protective layer 260 may be
disposed on the front side 210 of the remote phosphor tape to
protect the phosphor layer 230. Additional layers may also be
included in the phosphor tape. At least one of the substrate layer
235 or the protective layer 260 may be substantially transparent to
visible light, such that excitation light may reach the phosphor
layer and light generated by the phosphor layer may exit the remote
phosphor tape. Any of the phosphor layer 230, substrate layer 235,
release liner 250, or protective layer 260 need not be continuous
layers. In particular, the phosphor layer need not be continuous.
Some regions of the substrate layer may be coated with phosphor
material while other regions are not coated. For example, the
phosphor layer may be printed onto the substrate layer and the
phosphor materials may form a pattern on the tape.
[0038] FIG. 2C is an additional cross-sectional view of a remote
phosphor tape 200 mounted on a substrate 280. In some embodiments,
an adhesive 270, such as a pressure sensitive adhesive may be
provided on the substrate 280. The pressure sensitive adhesive 270
may be adjacent to a back side 220 of the phosphor tape 200. The
pressure sensitive adhesive 270 may be adjacent to a substrate
layer 235 of the tape. In alternate embodiments where a substrate
layer is not included, the pressure sensitive adhesive 270 may be
adjacent to a phosphor layer 230 of the tape. Alternatively, the
pressure sensitive adhesive may be adjacent to an optional release
layer 250 of the phosphor tape.
[0039] The substrate 280 may be coated continuously or selectively
with the adhesive 270. In some embodiments, it may be desirable to
have the adhesive in selected areas rather than covering the entire
back of the phosphor tape 200. Some regions of the substrate may be
coated with adhesive while other regions are not coated. Some
regions of the substrate to be covered by the phosphor tape may be
coated with adhesive while other regions are not coated.
Alternatively, the entire surface of the substrate or the surface
of the substrate to be covered with the phosphor tape may be coated
with the adhesive. For example, adhesive 270 may be printed on the
substrate 280 and the tape may be provided on the adhesive.
[0040] Adhesive may be provided directly on the remote phosphor
tape 200, on the substrate 280 upon which the tape is mounted, or
both. Any description of adhesive mounting on one surface may also
apply to another. The adhesive may or may not be continuous. In
some embodiments, the adhesive may be provided discontinuously and
may provide fixed mounting points. Fixed mounting points may allow
flexation between the points. In some instances flexation may be
desirable to accommodate various substrate morphologies or heat
effects.
[0041] In some embodiments, the remote phosphor tape comprises a
substrate layer that is reflective. The substrate layer may be
diffusely or specularly reflective, for example. The addition of a
reflector in the phosphor tape allows for enhancements in
efficiency. The excitation light that is not absorbed by the
phosphor layer and would otherwise be wasted, is reflected back
into the phosphor layer, increasing the effective path length of
the excitation light through the phosphor, such that the light
absorption by the phosphor is increased for a given thickness.
Thus, the phosphor layer thickness can be reduced, because the
reflector increases the efficiency of light generation in the
phosphor layer.
[0042] An additional loss in phosphor converted LED (pcLED)
efficiency occurs due to the directionally uncontrolled light
generation in the phosphor layer. A pcLED may be an LED that has a
fluorescent/phosphorescent material to convert a portion of the
light emitted by an LED chip to one or more other wavelengths. In
some embodiments, a pcLED may be a white LED. The phosphor material
absorbs light from the LED and re-emits it at a different, longer
wavelength such that white light can be obtained. However, about
half the photons produced by the phosphor are diverted back toward
the LED chip where much of the light is lost due to absorption. By
disposing the phosphor layer onto a reflective substrate layer, the
light generated by the phosphor can be directed from this base
reflector towards and optical element configured to distribute the
light.
[0043] The remote phosphor tape is configured to be used as a
remote phosphor in a lighting unit. Thus, the loading of the
phosphor in the remote phosphor tape can be greater than in a
device in which the remote phosphor tape is to be applied directly
to the LED package, and the index of refraction of the binder
material as well as the width and thickness of the remote phosphor
tape may be different than such a tape used for LED
encapsulation.
Methods of Making
[0044] The remote phosphor tape can be fabricated by disposing a
combination of one or more phosphor materials onto a substrate
layer in various ways, including evaporation, spray deposition,
sputtering, titration, baking, painting, printing, drawing, dip
coating, or other methods known in the art, for example. In some
embodiments, the substrate layer may comprise grooves, pockets, or
knobs into or onto which the phosphor material is disposed to
control the optical distribution of the light emitted by the
phosphor material.
[0045] The remote phosphor tape can also be formed by mixing a
phosphor material with a binder material and either disposing this
mixture onto a substrate layer or drawing the mixture into a tape
form. The binder material may be a silicone, for example.
[0046] In cases where the phosphor is deposited onto a substrate
layer, the phosphor layer can be uniquely tailored. In one
embodiment, an inkjet printer is used to deposit phosphor onto the
substrate layer. The inkjet printer may have a combination of one
or more phosphor inks that can be deposited at precise locations on
the tape. The inkjet printer can be used to deposit ink in the form
of dots, dashes, or lines of various widths. In some embodiments,
as phosphor may be printed, it may also be possible to print
adhesive in selected areas. For example, an inkjet printer can
deposit adhesive at precise locations on a tape or substrate. The
inkjet printer can deposit the adhesive in the form of dots,
dashes, or lines of variable widths.
[0047] This can be used to make remote phosphor tape that can
correct device to device color inconsistency. For example, in a
group of white lighting units, the product to product color
characteristics may vary depending upon the color characteristics
of the white LEDs supplied to create the product. A remote phosphor
tape can be used to create "warmer" white light that matches the
color characteristics (CRI and CCT) of other products manufactured.
Thus, a lighting device manufacturer is not restricted to a certain
supplier or bin from which to purchase the LEDs that go into their
lighting unit. Less expensive, surplus bins can be used with the
specially tailored remote phosphor taper providing color
correction.
[0048] The thickness of the phosphor layer can be tailored
dependent on the phosphor concentration such that absorption of
excitation light and emission of phosphor-converted light are
maximized.
[0049] FIG. 3 is a perspective view of a roll of remote phosphor
tape 300. In some embodiments, the remote phosphor tape may be
flexible such that it can be rolled as shown in FIG. 3. For
example, a remote phosphor tape comprising a polymeric binder and
phosphor may have a polymeric binder material that is flexible. In
another example, a remote phosphor tape may comprise a substrate
layer with a phosphor layer disposed adjacent to the substrate
layer. Both layers may be flexible and allow rolling of the remote
phosphor tape. Remote phosphor tape comprising a pressure sensitive
adhesive layer may further comprise a release liner.
[0050] The remote phosphor tape may be configured to be cut to
obtain a smaller piece of tape with dimensions appropriate for
positioning the remote phosphor tape within a particular lighting
unit. The remote phosphor tape may be made with lengths of
millimeters to tens of meters long, and may have widths ranging
from millimeter scale to a few meters wide. The tape can be
fabricated with a width and/or a length compatible with a dimension
desired for application in a lighting unit. For example, for
application in a fluorescent tube replacement, the remote phosphor
tape may have a length of 48 inches, for example, and a width of a
few millimeters, such that the tape does not need to be cut into
smaller pieces, or a larger width, requiring cutting of the tape to
dimensions appropriate for the application of the remote phosphor
tape in the lighting unit.
Methods of Using
[0051] The remote phosphor tape may be disposed on a support
structure in a lighting unit. In an LED device, the support
structure may be configured to provide support to the remote
phosphor tape such that the remote phosphor tape can be spatially
separated from the LED device package. The support structure may
also serve as an optical component. For instance, the support
structure may be a lens, reflector, or a diffractor.
[0052] In the exemplary embodiments that follow, a remote phosphor
tape is disposed on a support structure in a lighting unit. The
lighting unit comprises light emitting elements that are spatially
separated from the remote phosphor tape. The light emitting units
and the phosphor material in the remote phosphor tape phosphor
layer are chosen such that the light emitting unit emits at least
some light of a wavelength that can be used to excite at least some
of the phosphor material in the remote phosphor tape. The phosphor
material is configured to absorb this excitation wavelength and
re-emit the absorbed radiation as light of a different, generally
longer, emission wavelength. Thus, the phosphor is used to
color-convert at least some of the light generated by the light
emitting elements.
[0053] In embodiments described herein, the lighting unit comprises
a light emitting element such as a light emitting diode (LED) or a
laser diode which is configured to emit light of a first wavelength
when illuminated. The light emitting element may be a white light
emitter, a UV, or blue light emitter, for example. In addition to
light of a first wavelength, the light emitting element may emit
light of other wavelengths as well. For instance, the light
emitting element may be a white light LED that comprises an LED
that emits blue light and a yellow phosphor. The yellow light
emitting phosphor is in a silicone or epoxy that surrounds the LED
package. The yellow phosphor receives the blue light and down
converts the light to a yellow light. The combination of blue and
yellow light appear substantially white to a human observing the
light output of the light emitting element package. The light from
the light emitting element is directed towards the remote phosphor
tape. Thus, the phosphor in the remote phosphor tape is excited by
the radiation of the first wavelength and then emits light of a
second, different wavelength. Usually, the phosphor will
down-convert the light, meaning the excitation wavelength, or the
first wavelength, will be a higher energy (shorter wavelength) than
the light emitted by the phosphor or second wavelength.
Up-conversion of light is possible.
[0054] The conversion of light from one wavelength to another can
be used to modify the color characteristics of the lighting unit.
For instance, when a cool or bluish white light emitting element is
used in a lighting unit and a warmer white light is desired, the
remote phosphor tape can be added to the device to down convert
some of the light of the blue wavelength to a warmer color such as
orange or red. Color rendering index, color temperature, and color
consistency can be affected by use of a remote phosphor tape.
[0055] The light emitting elements may be cold cathode fluorescent
lamps (CCFLs) or electroluminescent devices (EL devices). Cold
cathode fluorescent lamps may be of the type used for backlighting
liquid crystal displays and are described generally in Henry A.
Miller, Cold Cathode Fluorescent Lighting, Chemical Publishing Co.
(1949) and Shunsuke Kobayashi, LCD Backlights (Wiley Series in
Display Technology), Wiley (Jun. 15, 2009). EL devices include high
field EL devices, conventional inorganic semiconductor diode
devices such as LEDs, or laser diodes, as well as OLEDs (with or
without a dopant in the active layer). A dopant refers to a dopant
atom (generally a metal) as well as metal complexes and
metal-organic compounds as an impurity within the active layer of
an EL device. Some of the organic-based EL device layers may not
contain dopants. The term EL device excludes incandescent lamps,
fluorescent lamps, and electric arcs. EL devices can be categorized
as high field EL devices or diode devices and can further be
categorized as area emitting EL devices and point source EL
devices. Area emitting EL devices include high field EL devices and
area emitting OLEDs. Point source devices include inorganic LEDs
and edge- or side-emitting OLED or LED devices. High field EL
devices and applications are generally described in Yoshimasa Ono,
Electroluminescent Displays, World Scientific Publishing Company
(June 1995), D. R. Vij, Handbook of Electroluminescent Materials,
Taylor & Francis (February 2004), and Seizo Miyata, Organic
Electroluminescent Materials and Devices, CRC (July 1997). LED
devices and applications are generally described in E. Fred
Schubert, Light Emitting Diodes, Cambridge University Press (Jun.
9, 2003). OLED devices and applications are generally described in
More recent developments in OLED materials and applications are
generally described in Kraft et al., Angew. Chem. Int. Ed., 1998,
37, 402-428, and Z., Li and H. Meng, Organic Light-Emitting
Materials and Devices (Optical Science and Engineering Series), CRC
Taylor & Francis (Sep. 12, 2006).
[0056] The light emitting elements can produce a colored light, a
UV or near-UV light, or a visually substantially white light. The
light emitting elements can emit light of a plurality of
wavelengths and their emission peaks can be very broad or narrow.
The light of an excitation wavelength refers to a portion of light
generated by the light emitting elements that can be color
converted by the phosphor material in the remote phosphor tape. It
is understood that there can be a plurality of wavelengths emitted
by the light emitting elements that can fit this criteria,
dependent upon the absorption profile of the phosphor material. It
is also understood that the phosphor layer, comprising a
combination of one or more phosphor materials, may comprise more
than one phosphor material that have overlapping absorption
spectra.
[0057] FIG. 4 is a schematic cross-sectional view of a remote
phosphor tape 410 being applied to an example support structure 420
in an illustrative lighting unit 430. In this example, the lighting
unit comprises light emitting element 440 such as an LED. The light
emitting element 440 may be positioned in an optically reflective
cavity 450 to reflect light up and out of the lighting unit 430.
The remote phosphor tape 410 can be disposed on the support
structure 420 with an adhesive, tacks, screws, or some other
mechanical coupling device. In some embodiments, an adhesive may be
applied to the phosphor tape, may be applied to the support
structure, may be applied to both the phosphor tape and support
structure, or is not applied to either the phosphor tape nor the
support structure. Any connection mechanism may be used to affix or
attach the phosphor tape to the support structure.
[0058] The support structure 420 in this illustrative lighting unit
430 is generally substantially transparent to visible and near-UV
light, however in other embodiments, the support structure need not
be transparent. The light emitting element 440 may be a near-UV
emitter, a blue emitter, or a white LED, for example. In the case
of a white LED, the LED may comprise a blue emitting LED chip
coated with a yellow phosphor, for example. In this example, the
lighting unit will have a hybrid package-level/remote phosphor
approach. The advantage of using such an approach is that improved
color can be obtained and maintained with higher efficiency and
longer lifetime. Red phosphors are generally the least efficient
phosphors and their lifetimes and efficiency are reduced further
when subjected to high temperatures. Thus, efficiency and lifetime
gains with improved color can be obtained when phosphors are
operated "remotely", or displaced from the high temperature LED
package.
[0059] The support structure may be a transparent mechanical
support configured to provide support to the remote phosphor tape
when mechanically connected thereto. Additionally, the support
structure can serve as an optical component. For example, the
support structure may comprise a combination of one or more
refractive, reflective, or diffractive elements configured to
direct light generated by the light emitting element or the
phosphor material towards another optical element or out of the
lighting unit to a region of desired illumination.
[0060] The support structure need not be a continuous support, but
may be a frame, or grid, for example. Alternatively, the support
structure may be a continuous support. Adhesive may be applied to
the tape or the support. In some instances, it may be desirable to
apply adhesive to the support rather than the tape when the support
structure is discontinuous or has an irregular shape. Exposed
adhesive on tape may attract dirt and impair performance. In some
embodiments, if portions of the tape are exposed and not covered by
the support, it may be desirable to provide adhesive on the
support. In contrast, if portions are the support are exposed and
not covered by the tape, it may be desirable to provide adhesive on
the tape.
[0061] The remote phosphor tape of an appropriate length may be cut
from a roll of remote phosphor tape. A release liner may be removed
from the back of the remote phosphor tape to expose the pressure
sensitive adhesive layer. The tape may then be applied to the
support structure as shown in FIG. 4 by pressing the tape onto the
support structure. The remote phosphor tape may comprise a
substantially transparent to visible light polymeric binder and a
phosphor, with or without a transparent substrate layer.
Alternatively, the remote phosphor tape may comprise a phosphor
sputtered onto a substrate layer, for example.
[0062] The lighting unit may comprise any combination of LEDs
emitting light of various colors, including white LEDs. For
example, the lighting unit may comprise white and red LEDs with a
remote phosphor tape comprising an orange or green phosphor, for
instance. In another example, the lighting unit may comprise red,
green, and blue LEDs with a color-correcting remote phosphor tape
that comprises a combination of down-converting phosphor materials
to achieve desired CCT and CRI, for example. In another example,
the lighting unit may comprise a near-UV emitting LED and a remote
phosphor tape comprising a combination of red, blue and green
emitting phosphor materials, for example.
[0063] In each example, in the illustrative lighting unit shown in
FIG. 4, the light emitting element is configured to be powered by
an external power supply and when illuminated, emit light of at
least one excitation wavelength. The light emitting element and the
remote phosphor tape are positioned such that the remote phosphor
tape is not in contact with the light emitting element package and
such that the phosphor layer receives at least a portion of the
light of at least one excitation wavelength. The phosphor material
is selected such that the light of a at least one excitation
wavelength excites the phosphor material and the phosphor material
down-converts the absorbed light of at least one excitation
wavelength to light of at least one emission wavelength which is
light of a longer wavelength and lower energy. In general, the
phosphor material is selected such that this phosphor conversion
process happens efficiently.
[0064] The light emitting element may emit light that does not
excite the phosphor layer in addition to the light of at least one
excitation wavelength. For example, in a lighting unit of white
LEDs, the LEDs emit light in the wavelength range of red light, but
this light does not excite an orange phosphor, for example.
However, the light of at least one excitation wavelength may
comprise light in the blue and green wavelength ranges that is
emitted by the white LED.
[0065] In the example in FIG. 4, the pressure sensitive adhesive
layer of the remote phosphor tape is applied to the external
surface of the support structure, such that excitation light from
the light emitting element passes first through the support
structure and then through the pressure sensitive adhesive layer,
any substrate layer, and then the phosphor layer. In another
embodiment, the phosphor tape may be disposed on the internal
surface of the support structure. In this case, the excitation
light from the light emitting element will pass first through any
protective layer, the phosphor layer, any substrate layer, or
adhesive layer, and finally the support structure. In both cases,
for this illustrative device, the support structure and the remote
phosphor tape should be substantially transparent to visible light
such that light from the light emitting element that is not
absorbed by the phosphor layer and light generated by the phosphor
layer can escape from the lighting unit. In order to enhance
efficiency of the lighting unit, reflective components surrounding
the light emitting element can be incorporated into the device. For
example, a reflective cone or side walls and a reflective mount 450
can reflect be used to re-direct high angle light from the light
emitting element to the phosphor layer. Additionally, light
generated by the phosphor layer that is emitted back toward the
light emitting element can be re-directed such that the light
passes through the phosphor layer again.
Methods of Using Reflective Remote Phosphor Tape
[0066] FIG. 5 is a schematic cross-sectional view of an
illustrative lighting unit 500 using the remote phosphor tape 510
as a remote phosphor material. In this embodiment of the invention,
the remote phosphor tape 510 is a reflective remote phosphor tape.
The remote phosphor tape comprises a diffusely reflective substrate
layer 520 upon which a phosphor layer 530 is disposed. The remote
phosphor tape 510 is disposed on a support structure 540. The
reflective substrate layer reflects light emitted by a light
emitting element 550 and the phosphor layer 530, back into the
phosphor layer 530 and out of the lighting unit. In this case, the
support structure 540 and the reflective substrate layer 520 need
not be substantially transparent, however, any protective layer
disposed adjacent to the phosphor layer should be substantially
transparent to visible light.
[0067] In a similar, alternative embodiment, the lighting unit
comprises a support structure with a reflective surface. A remote
phosphor tape with either a transparent substrate layer or without
a substrate layer is disposed on the reflective surface of the
support structure.
[0068] FIG. 6a is a perspective view and FIG. 6b is a schematic
cross-sectional view of another example of a lighting unit 600
comprising a remote phosphor tape within a lighting unit. The
lighting unit 600 depicted in FIG. 6a and FIG. 6b can be used, for
example, as a fluorescent tube replacement lamp. In this
embodiment, the lighting unit 600 comprises a lighting strip 610
having a plurality of light emitting elements 620. The light
emitting elements 620 are disposed along the length of a heat sink
630. The light emitting elements 620 in this example can be side
emitting light emitting diodes (LEDs) mounted on a circuit board
622, although in other examples, they can be mounted directly on a
heat dissipating support structure. The light emitting elements may
be electrically connected to one another. The light emitting
elements are configured to be powered by a power supply. The power
supply is generally an external power supply, though the power
supply may be incorporated within the lighting unit. The power
supply provides a drive condition which is a drive voltage or
current appropriate to power at least some of the light emitting
elements. The drive conditions can vary with time and can be
programmed to change in response to feedback from a sensor or user
input.
[0069] The LEDs are positioned such that light generated by the
LEDs is directed towards a remote phosphor tape 650 disposed on a
support structure 640. The remote phosphor tape 650 may be a
reflective phosphor tape having a reflective substrate layer that
directs light passing through and generated by the phosphor layer
towards an optical element 660. The optical element 660 is
configured to distribute the light as desired. In an alternative
embodiment, the remote phosphor tape 650 may be a substantially
transparent remote phosphor tape 650 disposed on a support
structure 640 with a reflective component. The support structure
640 can be specular or diffusely reflective. The support structure
may be at least partially reflective. It may have a continuous,
substantially reflective surface, or may have regions that are
reflective and regions that are not reflective or only partially
reflective. In some instances, an adhesive may be provided between
the phosphor tape and the support structure. In some instances,
when only portions of the support structures are reflective, it may
be desirable to provide adhesive only between non-reflective
portions of the support structure and the phosphor tape.
Alternatively, adhesive may be provided between any portions
between the support structure and the phosphor tape.
[0070] The support structure may be thermally conducting, or may be
disposed on a thermally conductive material, such as aluminum, so
that heat generated by the phosphor material due to Stokes shift is
conducted away. Thermal management at the phosphor material
location can reduce thermal quenching of the quantum efficiency of
the phosphor material and increase overall luminescence
efficiency.
[0071] The lighting unit may have one or more optical elements 660
to distribute light in a region or regions of desired illumination.
The optical elements may be light reflecting components, light
refracting components, light diffracting components, or a
combination thereof. The optical element may have a diffuser, a
lens, a mirror, optical coatings, dichroic coatings, grating,
textured surface, photonic crystal, or a microlens array, for
example.
[0072] The optical element may be any reflective, refractive, or
diffractive component, or any combination of reflective,
refractive, or diffractive components. For instance, the optical
element may be both reflective and refractive. For example, a
transparent optical element may be used which reflects light off of
the first optical surface and refracts light passing through the
optical element. Light reflection off the first optical surface
(the surface facing the base reflector) can be enhanced, for
example, by deposition of a thin, semi-transparent metallic layer.
Light refraction through the optical element is reflective coating
on the first optical surface of the optical element. The balance of
reflection and refraction can be tuned through the use of various
optical coatings on the first optical surface of the optical
element. Another example of a reflective and refractive optical
element is a transparent optical element with mirrors spatially
distributed on the first optical surface.
[0073] A reflective and refractive optical element may be
advantageous for providing direct and indirect lighting. For
example, with direct/indirect lighting, the lighting unit can emit
light both "up" to the ceiling and "down" to the workspace. Thus, a
good balance between ambient illumination of the room and accent
lighting at good energy efficiency can be achieved, even in large
spaces. Additionally, reflective glare on surfaces such as computer
screens is reduced with indirect lighting, and three dimensional
objects are rendered well without harsh shadows with indirect
lighting. Another example of achieving direct/indirect lighting is
to have a reflective optical element with holes or cutouts. Such an
optical element can reflect a portion of the light "down" to the
workspace, for example, as direct lighting from the lighting unit.
Another portion of light will be transmitted "up" through the holes
or cutouts in the optical reflector, to illuminate the ceiling, for
example, and provide indirect lighting from the lighting unit.
Directional "up" and "down" references are used herein only as
examples and other configurations and orientations of the lighting
unit are possible.
[0074] The shape of the optical element can define the distribution
of light from the lighting unit. Additionally, the curvature or
mounting angle of the optical element with respect to the position
of the base reflector and light emitting elements can define the
distribution of light from the lighting unit. For instance, in the
lighting strip 610 in FIG. 6b, the optical element 660 can be a
reflective optical element. The reflective optical element can be
made of a plastic support 662 with a thin, diffusely reflective
coating 664 disposed on the first optical surface which is the side
of the plastic support facing the support structure 640 and the
remote phosphor tape 650. The curvature of the optical element 660
can be configured to provide a broad distribution of light. Rather
than a continuous reflective coating, the optical element can
comprise reflective regions on the interior surface of the optical
element. Furthermore, the optical element can be an extension of
the heat sink support, for example. The reflective regions can be
made, for example, by polishing the interior surface of an aluminum
heat sink or by deposition of a thin reflective film on an aluminum
heat sink surface. Additionally, the shape or configuration of the
optical element can be changed to achieve a different distribution
of light. For example, the radius of curvature of the optical
element may be reduced in order to achieve a narrower distribution
of light. Light directed towards the optical element may experience
multiple reflections off of the optical element before being
directed towards another optical element or exiting the lighting
unit. Additionally, optical elements can be specular reflective
material or diffuse reflective material. Diffuse reflective optical
elements can further aid in broadening the distribution of
light.
[0075] In some embodiments, the optical element is a refractive
optical element such as a lens. For example, in FIG. 4, a lighting
unit 400 has a support structure 420 which may also serve as a lens
used to distribute light generated by the phosphor material 410 and
light emitting elements 440. The lens can be shaped to provide a
broad or narrow distribution of light. Refractive optical elements
can be diffusers to aid in providing a more uniform light
distribution. In some embodiments, there is a combination of one or
more optical elements that work together to homogenize and
distribute the light. For instance, in FIG. 4, reflectors 450 are
angled to direct light through or from the lens 420.
[0076] Using optical elements, a very broad distribution of light
can be achieved from even point source light emitting elements.
Thus, a highly efficient, diffuse light source can be obtained. A
major limitation of many state of the art LED lamp replacements is
that LED point source emitters are used and the light is not
adequately spread to provide a pleasant lighting experience. The
LEDs are directly viewable or covered only by a low efficiency
refractor. This provides harsh light with potential for glare and
little control over the beam distribution. Furthermore, color
quality and color consistency are limited by the LEDs.
Light Distribution
[0077] To achieve superior light distribution using a reflective
remote phosphor tape, the light emitting elements may be positioned
such that light emitted by the light emitting elements is directed
towards the phosphor material. The excited phosphor material emits
light of a longer wavelength. This light is emitted in multiple
directions from the phosphor material. Some of the light emitted by
the phosphor material will travel in a direction away from the
reflective substrate layer or support structure, and may leave the
lighting unit or be reflected or refracted by an optical element.
Some of the light emitted by the phosphor material will travel
towards the reflective substrate layer or support structure which
is positioned to reflect the light out of the lighting unit or
towards an optical element. Light from the light emitting elements
that is not absorbed by the phosphor material is also reflected by
the reflective substrate layer or support structure and directed
out of the lighting unit or towards an optical element.
[0078] The reflective substrate layer or support structure may
comprise means of directing light emitted from the phosphor
material. For example, the reflective substrate layer or support
structure may have a photonic crystal structure, or lens shaped
pockets upon which the phosphor material is disposed. Such
structures may aid in directing light emitted from the phosphor
material to the optical element, for example.
[0079] In some embodiments there is no optical element, so the
light distribution is controlled by the position and shape of the
reflective substrate layer or support structure. The reflective
substrate layer or support structure can have optical features to
aid in appropriately directing the light. For example, the
reflective substrate layer or support structure can have reflective
dimples or mounds, index-adjusting surface coatings, or other
features to direct unconverted light from the light emitting
elements and light from the phosphor material towards the optical
element or out of the lighting unit.
Narrow Support Structure
[0080] In some embodiments, a lighting unit is provided that has a
remote phosphor tape mounted on a narrow support structure. FIG. 7
shows an example of such a lighting unit 700. The lighting unit may
have a lighting strip comprising at least one light emitting
element, a heat dissipating support structure, a phosphor material,
and optionally one or more optical elements to achieve a desired
distribution of light. The remote phosphor tape may be attached to
a support structure such that the phosphor hangs from the support
structure. In some embodiments, if a portion of the tape is hanging
over the support structure, it may be desirable to provide adhesive
on the support structure, rather than on the tape. In some other
embodiments, if a portion of the support structures uncovered by
the tape, it may be desirable to provide the adhesive on the tape
rather than the support structure. Alternatively, adhesive may be
applied on either surface, both surfaces, or neither surface.
[0081] FIG. 7 shows a cross-sectional view of a lighting unit 700
having two lighting strips 710 each having its own array of light
emitting elements 720 and having a shared remote phosphor tape 730
that is attached to a support structure 740. The phosphor material
730 can be embedded in or disposed on an at least partially
transparent plastic strip, for example. The lighting strips 710 can
also share a common reflective optical element 750 and a common
refractive optical element 760, for example.
Advantages
[0082] The embodiments described herein are unique and offer
significant performance and cost advantages. The remote phosphor
tape allows for a highly efficient lighting unit with low cost,
improved light distribution and superior color characteristics
including color quality such as desired CRI and CCT, and color
consistency, device-to-device and over time. The remote phosphor
tape also importantly facilitates incorporation of phosphor
material in a lighting unit and can be tailored to provide
consistent and well controlled amount and thickness of phosphor
material amongst lighting units. Methods may be employed to dispose
various amounts of different phosphor material on the tape to
provide for the desired color adjustment in a lighting unit.
[0083] Aspects of the invention allow for a highly efficient
lighting unit. The efficiency of the lighting unit will be a
function of the LED efficiency, the thermal management, the
phosphor material down conversion and scattering, and the optical
efficiency of the system. In a system using the remote phosphor
tape to achieve a desirable warm light for general illumination
from cool white LEDs, the use of a phosphor on the LED chip and a
warming remote phosphor on a reflective substrate layer or support
structure will reduce the thermal quenching of the red and/or
orange phosphors which are the most thermally sensitive phosphors
and may allow the use of even more thermally sensitive phosphors
which have higher conversion efficiencies.
[0084] Cost advantages of the invention are also significant. The
cost of the remote phosphor is reduced by depositing phosphor
material in concentrated spots or strips on a tape and then
reflecting the light for distribution. The amount of phosphor
material in the phosphor tape can be well controlled, and material
is not wasted by trying to dispose the phosphor directly on a
lighting unit by means of solution or vapor deposition techniques.
With the excitation light directed to the remote phosphor tape, the
phosphor material can be concentrated in a narrow strip, saving
material costs. Diffuse light can be obtained when the phosphor
layer is disposed adjacent to a reflective surface, for instance.
The hybrid phosphor approach of using white phosphor converted LEDs
with a phosphor on or in the package in combination with a remote
phosphor tape further to achieve white light of desirable color
characteristics also can reduce the amount of phosphor needed and
hence the cost of manufacture, while improving the efficiency of
the devices. Other approaches that incorporate remote phosphor
throughout the lens help to get diffuse light, but require
significantly more phosphor material which can lead to prohibitive
costs.
[0085] In addition to cost and efficiency advantages, aspects of
the invention can provide improved light output, light
distribution, color quality, and color consistency. The use of
primarily reflective optics makes it much easier to tune the light
distribution, particularly with the use of two reflective surfaces.
For color control, homogenization of the cool white output from the
LEDs can be accomplished by the controlled use of LEDs with
different specific color points. The combined output of these LEDs
can be tuned to meet a consistent color point. By using a remote
phosphor tape, the specific amount of red and/or orange phosphor
materials can also be controlled to adjust the light output. The
multiple reflections can also evenly distribute the colors with
respect to output angle. Because phosphor materials of the red
and/or orange wavelengths are typically most sensitive to heat,
locating the phosphor remotely allows for slower degradation and
improved lifetime and efficiency of the red and/or orange phosphor
which will allow the color set point to be maintained for
longer.
EQUIVALENTS
[0086] While the invention has been described in connection with
specific methods, embodiments, and apparatus, it is to be
understood that the description is by way of example and not as a
limitation to the scope of the invention as set forth in the
claims.
[0087] It should be understood from the foregoing that, while
particular implementations have been illustrated and described,
various modifications can be made thereto and are contemplated
herein. It is also not intended that the invention be limited by
the specific examples provided within the specification. While the
invention has been described with reference to the aforementioned
specification, the descriptions and illustrations of the preferable
embodiments herein are not meant to be construed in a limiting
sense. Furthermore, it shall be understood that all aspects of the
invention are not limited to the specific depictions,
configurations or relative proportions set forth herein which
depend upon a variety of conditions and variables. Various
modifications in form and detail of the embodiments of the
invention will be apparent to a person skilled in the art. It is
therefore contemplated that the invention shall also cover any such
modifications, variations and equivalents.
* * * * *